Use an eMMC to microSD adapter, then microSD to USB adapter and connect the eMMC to the Windows system.

On a Windows system unzip the kali-*-odroidc2.img.xz file with 7zip

Use Win32DiskImager to write the Kali image to the eMMC.

For Linux

Use an eMMC to microSD adapter, then microSD to USB Adapter and connect the eMMC to the Linux system.

Use the dd tool to image the Kali file to the eMMC (It is very important that you choose the correct storage device here. It is very easy to accidentally wipe out your computers hard disk using this command. In the example below I use /dev/sdb but yours may be different so change accordingly.)